Netbotz dry contact electrical interface.

DCIM_Support · ‎2020-07-02

Hello everyone. We have a netbotz 570 with several PODs 155 (6) and 150 (2). On the model 150 POD we have installed five dry contact cables to monitor a fuel level sensor which has a corresponding relay closed on the dry contact cable (5 relays for full, 3/4, 1/2, 1/4, empty). As this fuel tank is far from the POD (about 25 meters) we have used a UTP cable conection, joining all common conections (black wire from the dry contac cable) and each of the red cables connect to the corresponding relay at the sensor. We have observed that this seems to be an "OR" setup, as if one of the contacts is closed the other show also as closed. Is the black wire really a common signal? or the contact closure is detected by current flowing on the black signal cable? Do you have documentation on how this dry contact sensor sensor works internally on the POD?

Thanks in advanced

Miguel Suarez

DCIM_Support · ‎2020-07-02

Hi Miguel,

The Dry Contact sensor, as well as the other state type sensors, will sit at 5v between the cable ends when the contacts are open and 0v when closed. These lines are fed back to an ADC which then determines the state based upon the voltage on the pins, if less than 2.5v the sensor is considered in a closed state.

These signal lines on the universal sensor ports are used for other probe types as you know, like the AP9335T or AP9335TH probes, so the internal circuitry is designed and used for multiple analog inputs.

That being said what you can do is simply switch your setup to use the Red wire as your common instead of the Black wire and you should be able to achieve the results you are looking for with each individual contact closure only creating a state change for its respective port.

See Answer In Context

DCIM_Support · ‎2020-07-02

Without knowing the internal circuit configuration of the 150 and the fact that you can connect different sensor types to each port, I would assume that you would have to use a separate pair of wires to connect each relay back to the 150.

DCIM_Support · ‎2020-07-02

Hello Richard, thanks for your answer. We can't really run another cable, it is not feasible. We would do it only if there is no other option because it involves high cost. We plan to withdraw the empty sensor because it has no so much sense (and put 1/4 sensor as critical alert) but would really like to know how the POD works internally.

Thanks

DCIM_Support · ‎2020-07-02

Hi Miguel, a UTP cable contains 8 cores so why not utilize these and only monitor 4 of the readings and do away with the fuel full alert? I have used UTP for dry contact extensions myself. Failing that use the UTP as a draw wire and replace it with a 12 core control cable.

DCIM_Support · ‎2020-07-02

Hi Miguel,

The Dry Contact sensor, as well as the other state type sensors, will sit at 5v between the cable ends when the contacts are open and 0v when closed. These lines are fed back to an ADC which then determines the state based upon the voltage on the pins, if less than 2.5v the sensor is considered in a closed state.

These signal lines on the universal sensor ports are used for other probe types as you know, like the AP9335T or AP9335TH probes, so the internal circuitry is designed and used for multiple analog inputs.

That being said what you can do is simply switch your setup to use the Red wire as your common instead of the Black wire and you should be able to achieve the results you are looking for with each individual contact closure only creating a state change for its respective port.

DCIM_Support · ‎2020-07-02

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